Tires: Tire balencing - types, Tire Balance

Question
I just came from my local tire shop, which is one of the better and faster ones in town (a community co-op).

I bought a pair of Michelins from them about a month ago and one of the kids working there talked me into putting all the weights on the inside of the rim for better looks.

Now today I had the tires re-balanced and the older guy who did it today said it is best to use weights on both sides,
which he referred to as dynamic balancing while weights on just one side (done with the same spinning tire machine --- forget the brand name of it) called it a static balance...

I must be old or remember when static balance was done with a bubble balance.. the older tire guy said that static is not worth the time....Now I agree and will soon test the results on the road.

Thanks for any input or explanation, like your other one posted on balancing.


Answer
John,

Balancing is a mass distribution problem.

Static balance only takes care of the imbalance in one plane.  It assumes the imbalance is centered on the tire.  This isn't a terrible assumption, but it isn't always true.  But putting the weights on the inside actually creates the other kind of imbalance - an off center imblance.

Dynamic balance is a 2 plane procedure.  It takes care if the mass is not centered on the tire.

In the old days, cars had sloppy suspensions, fairly flexible chassis's, and loose steering systems, so off center imbalnce was hardly noticeable.  Modern cars, with their stiffer chassis's and much more precise steering are not only more sensitive to off center imbalance, but tire and rim run out as well.

Hopefully, someone has corrected that kid you talked to, because I am sure there will be a lot of folks coming back with vibrations.